In U.S. Pat. No. 4,220,280, there is shown and described a manure spreader having a spreader box that is open at its rear end and in which the vertical side walls are connected by a floor composed of front and rear horizontal portions. The front portion is adapted to move rearwardly on the rear portion to a completely overlying position. A vertical push-off is provided to move rearwardly on the front portion. Consequently, in moving animal waste in the box to the open rear end of the spreader box, the material supported on the front floor portion is shifted rearwardly along with the push-off. The material on the front floor operates to move the material contained on the rear floor portion into the beaters at the rear end of the spreader box. Thereafter, when the front floor portion is in overlying relation to the rear floor portion, the push-off is operated to push the material off the front portion and into the beaters.
In such an arrangement as above described, it has been found necessary to provide, on the side walls and on the upper surfaces of the floor portions, plastic layers that are normally bonded to the underlying plywood or wood fiber boards. The plastic provides a smooth polished surface so that the animal waste contained in the box may more easily slide to the rear end of the box.
One of the problems that has been encountered in providing such a push-off type spreader is that the front floor portion carries considerable load when it moves rearwardly over the rear floor portion. Also, as the material on the front floor portion pushes against the material on the rear floor portion, there is additional weight added to the front portion and also a downward force component applied by the material on the rear portion to the front portion. This, of course, creates a considerable wear condition between the underside of the front portion and the upper side of the rear portion as the front portion moves rearwardly over the rear portion. Since the plastic layer is relatively thin, scouring and scratching of that surface often will penetrate completely through the layer so that the acidic parts of animal waste will penetrate into the plywood or the fibrous face of the rear floor portion. Once penetrated through the plastic surface, deterioration of the entire floor portion progresses rapidly.